Leveling valves of the aforementioned type are for example known from WO 2010/089089 or EP 2 806 194 A1.
Leveling valves of the known type are used to regulate the vertical clearance of a vehicle such as a truck or other utility vehicle with respect to ground level. Depending on the load situation of the vehicle or depending upon dynamic forces acting on the utilization elements such as pneumatic suspension bellows of a vehicle, it is in certain situations necessary to increase or decrease the suspension level of the utilization elements. This is achieved by switching the leveling valve, in particular the valve arrangement, from its neutral position to either an “exhaust” switching position or an “air supply” switching position. Depending on the switching position, air will be exhausted from the utilization elements into the atmosphere, or will be supplied to the utilization elements from a source of pressurized air.
The leveling valve known from WO 2010/089089 focuses on ways of decreasing the number of sealing elements used inside a valve by making a non-rotatable valve disc axially movable inside a valve housing, wherein the two valve discs are pressed against each other by pressure prevailing in either a line connected to the source of pressurized air or in a line connected to the utilization elements.
EP 2 806 194 focuses on providing an improved leveling valve with better reactivity when switched and with less noise emission. EP 2 806 194 suggests to employ rotatable valve discs for controlling the effective flow cross-section in a flow path between a source of pressurized air or the exhausted port in the utilization elements. In particular, it is suggested to provide a step increase in flow cross-section by means of the valve discs rotatable with respect to each other. Further, by providing a sudden increase in flow cross-section at low rotation angles, followed by a comparatively shallow increase at higher rotation angles, a good reactivity of the valve is achieved at low rotation angles, while the acoustic noise of the valve is reduced by means of the comparatively shallow increase at higher rotation angles of the rotatable valve discs.
While EP 2 806 194 achieves a noise reduction, there is still a need for further improvement.